New genetic evidence for the origins of castes indicates that the upper
castes are more European than Asian.

R. RAMACHANDRAN

THE caste-based social hierarchy is deeply entrenched in Indian society even
today, but the origins of the system as sociologists and historians now
understand, remain an enigma. It certainly goes as far back as the second
millennium B.C. when the Aryans, the migrating Indo-Iranian or Indo-European
people, entered the country from the northwest and drove southward the
proto-Asian and Dravidic speaking populations inhabiting the north. Literary
evidence for the stratification of the society, at least in terms of
references to the duties of the highest caste, namely the Brahmin, exists in
the oldest text of the land, namely the Rig Veda (1500-1200 B.C.). The
emergence of the caste system is thus associated with the arrival of the
Aryans.

However, many sociologists believe that some kind of a hierarchical social
order, in terms of an individual's occupation and duties, was in place
perhaps ahead of the arrival of the Aryans. Its evolution into the caste or
the varna system as we know today - with the four distinct castes of
Brahmin, Kshatriya, Vaisya and Sudra in the order of social standing -
probably occurred with the settling of the Aryans who sanctified and
legitimised the social order in their own terms which had a distinct
religious underpinning. Some sociologists hold that the societal
stratification in terms of rights and duties of the individual was a
creation of the Aryans in their bid to exercise power over the indigenous
proto-Asian populations of North India.

An anthropologically pertinent question, therefore, is what really are the
origins of the caste Hindu populations of today who make up nearly 80 per
cent of India's one billion population. In recent times, with the rise of
strident nationalism in the form of "Hindutva" ideology, which rejects the
premise that Aryans were outsiders and views them as part of the continuum
from the Indus valley civilisation, an unequivocal answer to this may have
political implications. While material evidence of ancient history has not
been able to resolve this issue, modern population genetics, based on
analyses of the variations in the DNA in population sets, has tools to
provide a more authoritative answer. Certain inherited genes carry the
imprint of this information through the ages.

An international study led by Michale J. Bamshad of the Eccles Institute of
Human Genetics of the University of Utah of caste origins has found (the
findings have been reported in a recent issue of the journal Genome
Research) that members of the upper castes are genetically more similar to
Europeans, Western Eurasians to be specific, whereas the lower castes are
more similar to Asians. This finding is in tune with the expectations based
on historical reasoning and the prevalent views of many social historians.
In exercising their superiority over native proto-Asian populations, the
Aryans would have appointed themselves to higher rank castes. The 18-member
research team includes scientists from the United States, the United
Kingdom, India and Estonia. The collaborating Indian scientists were
anthropologists Bhaskar Rao, J. Mastan Naidu and B. V. Ravi Prasad from
Andhra University, Visakhapatnam, and P. Govinda Reddy from the University
of Madras.

There have been genetic studies in the past that tried to answer this
question but their results have been equivocal, in the sense that some have
found European origins and some Asian origins. According to Partha P.
Majumder, a population geneticist with the Indian Statistical Institute
(ISI), Kolkata, who has written a commentary on the work in the same issue
of the journal, the primary reason for this was the lack of data on a large
uniform set of genetic markers from populations of India and central/west
Asia. This study, where the researchers have used a battery of genomic
markers and DNA sequences spanning three genomic regions, is a landmark,
says Majumder. "The study provides an incisive genomic view of castes and
their origins," he has written.

"It is conceivable that the Aryan contact should have been progressively
lower as one descended the varna ladder. The genetic expectation, therefore,
is that the proportions of those genes (or genomic features) that
'characterised' the Aryan speakers should progressively decline from the
highest varna to the lowest and a reverse trend should be observed with
respect to those genes that 'characterised' the indigenous Indians,"
Majumder says.

The three different genomic regions the study has looked at include two
gender-specific genes and one biparentally inherited gene. Mitochondrial DNA
(mtDNA), the DNA contained in mitochondria which are tiny organelles in each
cell that generates the energy required by the cell, is exclusively derived
from the mother. Similarly, the Y-chromosome, which defines the male gender
in mammals, is passed on exclusively by the father.

Interestingly, an analysis of the genetic variations in the markers
associated with the maternally inherited mtDNA and paternally inherited
Y-chromosome show strikingly different trends. Maternally inherited DNA was
overall found to be more similar to Asians than to Europeans, though the
similarity to Europeans increases as we go up the caste ladder. Paternally
inherited DNA, on the other hand, was overall more similar to Europeans than
to Asians but, unlike in the case of maternal inheritance, with no
significant variation in affinity across the castes. This is intriguing, but
there is a plausible explanation. Migrating Eurasian populations are likely
to have been mostly males who integrated into the upper castes and took
native women. Inter-caste marriage practices, while generally taboo, are
occasionally allowed, in which women can marry into an upper caste and move
up in the social hierarchy. However, such upward mobility is not permissible
for men. The caste labels of men are thus permanent, while women, by means
of their limited mobility, cause a gene flow across caste barriers. This is
the reason, according to the researchers, for the differing affinities of
gender-specific genes among castes to continental populations.

In fact, in a study carried out in 1997, the results of which were published
in 1998 in Nature, the same research group had mapped this female gene flow
among caste groups in Andhra Pradesh. Analogously, in 1999 Majumder and
colleagues examined the genetic impact of this social custom preventing
upward mobility of males in the caste hierarchy. They looked at six genetic
markers for the male inherited Y-chromosome and found that there was little
sharing between castes of the features pertaining to the markers. This
phenomenon has been described by Bamshad and company as "modulation of
evolutionary forces by social processes" instead of through the normal,
purely natural, processes of genetic drift and mutation.

Bamshad and associates examined 40 additional bi-parentally inherited genes
as well, which also confirmed the results obtained from mtDNA and
Y-chromosome markers that Hindu upper castes are genetically closer to
Europeans. They thus conclude that Indian caste Hindus "are more likely to
be of proto-Asian origin with West Eurasian admixture resulting in rank
related and sex-specific differences in their genetic affinities to Asians
and Europeans."

Basically the study carried out three sets of comparisons of genetic
variations respectively in the mtDNA, the Y-chromosome and the 40 specific
autosomal (of chromosomes other than the sex chromosomes X and Y) gene
sequences in a sample of 265 males, belonging to eight Telugu speaking
castes, from Visakhapatnam district. Comparisons were made within this
sample and to 400 individuals from tribal and Hindi-speaking populations
within the country and 350 Africans, Asians and Europeans.

The eight castes chosen were Niyogi and Vydiki Brahmin, Kshatriya, Vysya,
Telega and Turpu Kapu, Yadava, Relli, Madiga and Mala. Significantly, the
castes were ranked as 'upper', 'middle' and 'lower' instead of the
four-level hierarchy of the traditional varna classification. Such a
classification has in recent times apparently become more popular among
anthropologists. Brahmins, Kshatriyas and Vysyas were grouped as 'upper'
caste, Kapu and Yadavas as 'middle' caste and the remaining three as
'lower'. "In studies pertaining to origins of castes, one is liable to draw
incorrect inferences by including castes belonging to different varnas in
the same ranked cluster," points out Majumder.

For the extraction of DNA from the sampled population, after obtaining
informed consent, about 8 ml of whole blood or five plucked scalp hairs were
collected from each participant. The DNA extraction and its amplification by
the Polymerase Chain Reaction (PCR) technique was carried out at Andhra
University by Indian scientists. To conform to the ethical guidelines of
research with the human genome, approvals and clearances were obtained from
Andhra University and the Government of India, according to the authors of
the paper. (These DNA samples are being maintained by Andhra University
where a laboratory has been set up to carry out such analyses.)
Analysis of "genetic distances" - a measure of genetic similarity and
affinity - of markers of mtDNA, the maternally inherited DNA, between caste
populations and continental populations shows that, irrespective of caste
rank, each caste group is most closely related to Asians and is most
dissimilar from Africans. And as one moves from the lower castes to the
upper castes, the genetic distances to Asians increases, suggesting that
Indian populations are predominantly proto-Asian but with affinities to West
Eurasian genes. The West Eurasian admixture is, however, proportional to the
ranking among castes. Analysis of a special set of mtDNA markers (called
haplotypes), whose loci in the genome are closely linked and which tend to
get inherited together, also showed that the West Eurasian admixture
amounted to 20-30 per cent of mtDNA haplotypes.

Similar "genetic distance" analysis using the paternally inherited
Y-chromosome presented, as indicated earlier, a distinctly different pattern
of population relationships among castes and among castes and continental
populations. In contrast to the mtDNA distances, Y-chromosome data do not
suggest a closer affinity to Asians. The upper castes are more similar to
Europeans than to Asians, the middle castes are equidistant from the two
groups and the lower castes are most similar to Asians. The genetic
distances between caste populations and Africans increase as one moves from
lower to upper caste groups.

Looking at the variations in a particular special set of Y-chromosome
markers, the study disaggregates the European population into Northern,
Southern and Eastern Europeans. The analysis of genetic distances shows that
each caste is most closely related to Eastern Europeans. Moreover, the
genetic distance between Eastern Europeans and upper castes is half the
distance between the middle or lower castes and the Eastern Europeans. The
authors interpret this as the Indian Y chromosomes, particularly upper caste
Y-chromosomes, being more similar to European than to Asian Y-chromosomes.
One limitation of the study is the restricted geographical region, namely a
single district of Andhra Pradesh, from which the sample of caste Hindu
populations have been obtained. The likely reason is that of the logistics
of achieving rapport with local populations and getting their consent for
genetic analysis.

But according to the researchers this also helped in "minimising the
confounding effect of geographical differences between populations."
Moreover, the sample size of 265 is too small for drawing conclusions about
a Hindu caste population of about 800 million. For example, the number of
Kshatriyas in one comparison set is as small as 10. The authors do recognise
this limitation in their paper and emphasise the need for carrying out
similar analysis in other regions of the country. They, however, remark that
because of the ubiquity of the caste system, it is reasonable to predict
similar patterns in caste populations in other areas. But according to
Majumder, replicating the study in other areas is, in fact, imperative
before general conclusions about origins of Indian caste populations can be
drawn.

"It is not generally realised that the caste society in a sense was a very
elastic society and a caste bearing the same name may have very different
origins in different geographical regions," he points out. According to him
there are examples when a tribe dispersed over a large geographical region
took up different occupations in different sub-regions and fitted itself
into the caste hierarchy on different rungs. Different Brahmin castes of
Maharashtra, for example, probably had different origins, he says. "Thus,
the origin of caste populations may not be uniform over the entire country,"
adds Majumder. It is also reasonable to assume that northern societies are
more likely to reflect more truly the real origins of caste than societies
down south where Dravidic features are likely to be reflected in the
genetics of the populations. Also, several social forces may have interfered
to result in the stratification as is evident today.